TWI823860B - Light emitting device - Google Patents

Abstract

A light-emitting device is disclosed. The light emitting device includes an electron blocking layer, a hole blocking layer, wherein at least a portion of the hole blocking layer is arranged to have a compressive strain, and an active layer disposed between the hole blocking layer and the electron blocking layer.

Description

Lighting device

The present invention relates to light emitting devices, and more particularly, the present invention relates to strained AlGaInP layers for high efficiency electron and hole blocking in light emitting devices.

Light emitting diodes ("LEDs") are commonly used as light sources in a variety of applications. The main functional part of an LED may be a semiconductor wafer containing two injection layers of opposite conductivity types (p-type and n-type) and a light-emitting active layer for radiative recombination (in which carrier injection occurs). The composition of the injection layer and the active layer can be varied depending on the desired wavelength. For light emission in red to amber visible wavelengths, materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family can be used.

According to aspects of the present invention, a light-emitting device is disclosed, which includes an electron blocking layer, a hole blocking layer, and an active layer disposed between the hole blocking layer and the electron blocking layer. The light emitting device may be formed from materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system and/or any other suitable type of material. In some embodiments, at least a portion of the hole blocking layer can be configured to have a compressive strain. Additionally or alternatively, in some embodiments, the active layer can have at least one well structure including: a first barrier layer configured to have a tensile strain; a second barrier layer configured to have a tensile strain. having a tensile strain; and a well layer disposed between the first barrier layer and the second barrier layer.

Cross-references to related applications

This application claims the rights of U.S. Patent Application No. 15/662,952 filed on July 28, 2017 and European Patent Application No. 18152290.5 filed on January 18, 2018, the contents of which are incorporated by reference. into this article.

Examples of different light emitting diode ("LED") implementations are described more fully below with reference to the accompanying drawings. These examples are not mutually exclusive, and features found in one example may be combined with features found in one or more other examples to achieve additional implementations. Therefore, it should be understood that the examples shown in the drawings are illustrative only and are in no way intended to limit the invention. The same reference numbers refer to the same components throughout the drawings.

It should be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish elements from each other. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that when an element such as a layer, region, or substrate is referred to as being "on" or "extending over" another element, it can be directly on or extending directly over the other element. Or intervening elements may be present. In contrast, when an element is considered to be "directly on" or "directly extending directly onto" another element, there are no intervening elements present. It should also be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when one element is considered to be "directly connected" or "directly coupled" to another element, there are no intervening components present. It will be understood that these terms are intended to cover different orientations of the component in addition to any orientation depicted in the figures.

Relative terms such as “below” or “above” or “on” or “lower” or “horizontal” or “vertical” may be used herein to describe one element, layer or region in relation to another element, layer or region relationship, as depicted in the figure. It will be understood that these terms are intended to cover different orientations of the device in addition to the orientation depicted in the figures.

Group III-P semiconductor devices, such as those using the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, are produced from amber to red (eg, about 570 nm to about 680 nm) Visible light wavelength. The wavelength range of light is achieved by adjusting the aluminum to gallium ratio during the growth of the alloy.

Figure 1 depicts an example of a light emitting device 100 produced using the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system in accordance with aspects of the present invention. Device 100 includes a substrate 110 on which a strain-free hole blocking layer (HBL) 120 is formed. The substrate 110 includes an absorbing gallium arsenide (GaAs) substrate. The hole blocking layer (HBL) 120 is formed of an n-type material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system. An active layer 130 is formed above the HBL 120 . The active layer 130 has an ( _{AlxGa1 -x} ) _{1- yInyP} composition and includes a plurality of barrier layers 130a and well layers 130b configured to form a plurality of well structures. An electron blocking layer (EBL) 140 is formed above the active layer 130 . The electron blocking layer (EBL) 140 is formed of a p-type material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system. Contacts 150a and 150b are disposed on HBL 120 and EBL 140 respectively to provide means for biasing device 100 .

When a forward bias is applied to device 100, carriers are injected into active layer 130, where they recombine and convert their excess energy into light. Therefore, high-efficiency operation of device 100 depends on high-efficiency injection of carriers into active layer 130 and high-efficiency recombination of injected carriers within active layer 130 . In order to improve the efficiency of carrier recombination, the active layer 130 is configured to include a plurality of well structures. Each well structure is formed by a well layer 130b sandwiched between two barrier layers 130a. In some embodiments, each barrier layer 130a may be formed of a first ( _{AlxGa1 -x} ) _1- yInP material, and each well layer 130b may be formed of a second ( _{AlxGa1 -x} ) _1- yInP material. Material formation. In some embodiments, the first ( _{AlxGa1 -x} ) _1-y InP material can have an aluminum ratio in the range of 0% to 30% (0<x<0.3). Additionally or alternatively, in some embodiments, the second ( _{AlxGa1 -x} ) _1-y InP material can have an aluminum ratio in the range of 40% to 100% (0.4&lt;x&lt;1).

In some aspects, the amount of electron confinement provided by barrier layer 130a is determined by conduction band offsets (CBO) between barrier layer 130a and well layer 130b. Similarly, the amount of hole confinement provided by the barrier layer is determined by the valence band offsets (VBO) between the barrier layer 130a and the well layer 130b. For a high-efficiency active layer design, the CBO between barrier layer 130a and well layer 130b must be large enough to confine electrons in high current injection and high temperature operation of device 100. Similarly, the VBO between barrier layer 130a and well layer 130b must be large enough to confine holes in high current and/or high temperature operating environments.

In high temperature and/or high current operating environments, carriers may escape the active layer 130 despite the presence of well structures in the active layer 130 . To this end, EBL 140 and HBL 120 are provided on the side of the active layer 130 to supplement the function of the barrier layer 130a and prevent carriers from overflowing from the active layer 130. As will be discussed further below with respect to FIG. 2 , the degree of electron confinement provided by EBL 140 is proportional to the CBO between EBL 140 and the well structure within active layer 130 . Similarly, the hole confinement provided by HBL 120 is proportional to the VBO between HBL 120 and the well structure of active layer 130 .

In the examples of FIGS. 1 and 2 , HBL 120 is the lower localization layer (LCL) of device 100 and EBL 140 is the upper localization layer (UCL) of device 100 . However, in some embodiments, HBL 120 may be separated from the LCL of device 100. Additionally or alternatively, in some embodiments, EBL 140 may be separate from the UCL of device 100. In these examples, EBL and HBL may also be undoped or doped differently than UCL and LCL. Additionally or alternatively, in some embodiments, in addition to EBL 140, one or more other layers may be present in the UCL. Additionally or alternatively, in some embodiments, in addition to HBL 120, one or more other layers may be present in the LCL. Furthermore, it should be noted that device 100 is not limited to the layers described above, but may have additional epitaxial layers grown before or after active layer 130 . In this regard, HBL 120 may be any n-type layer in device 100 except active layer 130 . Similarly, EBL 140 may be any p-type layer in device 100 except active layer 130 .

Figure 2 is an energy band diagram 200 of device 100 in which the valence band (Vb) and conductive band (Cb) energies of layers 120-140 are plotted against their respective spatial locations. The energies of the conductive band Cb and the valence band Vb are determined by the chemical bonds of the atoms in the crystal lattice of layers 120 to 140. In this example, the conductive band Cb is defined by the lowest of the X-band and Γ-band energies of the electrons in layers 120 to 140.

As shown in the figure, band diagram 200 is divided into segments 220, 230a, 230b, and 240. Section 240 shows the valence band Vb and conductive band Cb of EBL 140 . Section 230a shows the respective valence band Vb and conductive band Cb of barrier layer 130a. Section 230b shows the respective valence band Vb and conductive band of well layer 130b. And section 220 shows the conductive band Cb and the valence band Vb of HBL 120 . Also shown in Figure 2 are the conductive band compensation CBO ₁ of EBL 140 and the valence band compensation VBO ₁ of HBL 120 relative to the active zone well material. As indicated above, the magnitudes of VBO ₁ and CBO ₁ determine the carrier localization limits in active layer 130 provided by HBL 120 and EBL 140 respectively.

The conductive band compensation CBO ₂ and the valence band compensation VBO ₂ are respectively the conductive band and the valence band compensation of the well structure formed by the barrier layer 130a and the well structure 130b. As shown in the figure, the band gap of well layer 130b is narrower than the band gap of barrier layer 130a, which allows carriers to move perpendicular to the crystal growth but not in the same direction. This in turn results in the higher concentration of charge carriers in the well layer 130b being localized and increasing the probability of radiative recombination.

As discussed above, the magnitude of CBO ₂ and VBO ₂ of well structures in active layer 130 determines the extent of charge carrier confinement provided by these structures. Generally speaking, _the maximum _conductive band compensation system that can be used for the _{( Al} 130a is achieved with an aluminum ratio (x) of 53%. This combination of aluminum (Al) and gallium (Ga) in well layer 130b provides an emission wavelength of about 650 nm to about 680 nm. In order to achieve shorter wavelength emission, the aluminum ratio (x) in the well layer 130b needs to be increased, which will reduce the conductive band and valence band compensation of the well structure in the active layer 130. Reduced band compensation will bring serious losses to the electron blocking and hole blocking capabilities of the well structure in the active layer 130 . This loss only increases at high injection and high temperature operations.

Figure 3 depicts an example of a light emitting device 300 designed to offset some of the losses associated with increasing aluminum content. The device 300 includes a substrate 310, a lower confinement layer (LCL) 320, an active layer 330, and an upper confinement layer (UCL) 340. According to this example, substrate 210 includes an absorbing GaAs substrate. Furthermore, according to this example, each of the LCL 320, the active layer 330, and the UCL 340 may be formed of a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system.

In some aspects, the conductive band energy of materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy series is affected by the aluminum ratio of the materials. More specifically, the _Γ band is _the lowest conductive band for materials from _the ( _Al And the alloy behaves as a direct bandgap material. In comparison, when the aluminum ratio in the (Al _x Ga _1-x ) _1-y In _y P alloy system is greater than 53% (0.53<x<1), the X band defines the active layer 330 and the Individual well structures and electronic localization in EBL (or UCL). Therefore, when the aluminum ratio is greater than 53% (0.53<x<1), the greater the energy level of the high.

One way of raising the energy level of the X-band of materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system is to induce a tensile strain in the crystal lattice of these materials. When the indium ratio is 49% (y=0.49), the material from the (Al _x Ga _1-x ) _1-y In _y P alloy system is lattice matched to the GaAs substrate when 0>x>1. When the indium ratio drops below 49% (0＜y＜0.49), materials from the (Al _x Ga _1-x ) _1-y In _y P alloy system can be formed on a GaAs or Si substrate. Tensile strains are induced in the material to properly adjust the lattice mismatch between the Si lattice and AlGaInP. If tensile strain is present, the energy of the Γ band of the material decreases relative to the conductive band edge at a rate of approximately 85 meV/GPa and the energy of the X band increases relative to the conductive band edge at a rate of 25 meV/GPa. The amount of X-band energy increase depends on the amount of tensile strain, but is limited by the critical thickness of the strained material.

Device 300 incorporates a tensile strained electron blocking layer to achieve improved electron confinement. As shown in Figure 3, UCL 340 includes a (p-type) tensile strained electron blocking layer 340a and a (p-type) unstrained electron blocking layer 340b. Tensile strained electron blocking layer 340a is formed from one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system and may have an indium ratio of less than 49% (0<y<0.49). The presence of less than 49% indium causes the accumulation of tensile strain in the crystal lattice of electron blocking layer 340a, which in turn may broaden its band gap and enhance its electron blocking capabilities. Additionally or alternatively, in some embodiments, electron blocking layer 340a may include an aluminum ratio greater than 53% (0.53<x<1).

Strain-free electron blocking layer 340b may be formed of one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system. In some embodiments, the indium ratio (y) of the unstrained electron blocking layer 340b may be equal to 49% (y=0.49), thereby causing the unstrained electron blocking layer 340b to be lattice matched to the GaAs substrate 310. Additionally or alternatively, in some embodiments, the aluminum ratio (x) of the unstrained electron blocking layer 340b may be in the range of 40% to 100% (0.4≤x≤1).

Turning to active layer 330, active layer 330 includes a plurality of strain barrier layers 330a and well layers 330b configured to form a set of well structures. Each well structure includes a well layer 330b disposed between two strain barrier layers 330a. At least some of the barrier layers 330a include a strained structure 330a-1 and an unstrained structure 330a-2, as shown in the figure. Each of the strained structures 330a _- 1 _may be derived from ( _{Al y} In _y P alloy system is formed of one of the materials. Each of the strained structures 330a-1 may have a thickness less than the critical thickness of the material from which they are formed to avoid relaxation. Each strain-free barrier layer structure 320a-2 may be formed from (Al _x Ga _{1- x} ) _1-y In _y P alloy system is formed of one of the materials. As discussed above, the presence of less than 49% indium in barrier layer 330a (or portions thereof) may induce the accumulation of tensile strain in the respective lattice of barrier layer 330a, thereby widening its bandgap and enhancing its electron-blocking capabilities. .

In some implementations, all barrier layers 330a may have the same thickness. Additionally or alternatively, in some implementations, at least two barrier layers 330a may have different thicknesses. In some embodiments, all well layers 330b may have the same thickness. Additionally or alternatively, in some embodiments, at least two well layers 330b may have different thicknesses. In this regard, the present invention is not limited to any particular absolute or relative physical dimensions of barrier layer 330a and well layer 330b.

Although in this example, barrier layer 320 depicted proximate HBL 320b includes a single unstrained structure 320a-1, alternative embodiments are possible in which barrier layer 320a depicted proximate HBL 320b includes in addition unstrained structure 320-1. In addition to 1, one or more strain structures are also included. Additionally, alternative embodiments are possible in which each barrier layer 320a consists of a single strained structure 320a-1. Furthermore, alternative implementations are possible in which any number of strained and/or unstrained structures are present in any of barrier layer 320a. In short, the present invention is not limited by the number and/or type of structures seen in any of barrier layer 320a.

As discussed above, at least some of barrier layer 330a and electron blocking layer 340a are strained to better confine electrons within active layer 330 and individual well structures within active layer 330. However, merely increasing the electronic limitations is not sufficient to operate device 300 efficiently. For high-efficiency operating devices, hole blocking is as important as electron blocking in high-temperature and high-current operations.

In order for HBL to block holes efficiently, the energy of the valence band should be reduced relative to the valence band of the quantum well to increase VBO1. In contrast to electron blocking, high efficiency hole blocking can be achieved by introducing a compressive strain into the lattice of the hole blocking layer. More specifically, the compressive strain of the (Al _x Ga _1-x ) _1-y In _y P material can be achieved by increasing the indium ratio (y) above 49% (0.49<y<1).

Device 300 incorporates a compressively strained hole blocking layer (HBL) 320b to achieve improved hole localization. More specifically, LCL 320 _is formed from a material _{in the} ( _Al Strained hole blocking layer 320b. The indium ratio of the strain-free hole blocking layer is 49% (y=0.49), which causes the strain-free hole blocking layer (HBL) 320a to lattice match the GaAs substrate 310. Compressive Strain The indium ratio of HBL 320b may be higher than 49% (0.49<y<1), which results in accumulation of compressive strain in hole blocking layer 320b. In some embodiments, the thickness of the compressively strained hole blocking layer may be less than the critical thickness of the material of the layer to avoid relaxation that would create defects in the crystal.

Figure 4 is an energy band diagram 400 of device 300 in which the valence band (Vb) and conductive band (Cb) energies of layers 320-340 are plotted against their respective spatial locations. As shown in the figure, band diagram 400 includes segments 420a, 420b, 430a, 430b, 440a, and 440b. Section 440b shows the valence band Vb and conductive band Cb of strain-free electron blocking layer (EBL) 340b. Section 440a shows the valence band Vb and conductive band Cb of tensile strained electron blocking layer (EBL) 340a. Section 430a shows the respective valence band Vb and conductive band Cb of strain barrier layer 330a. Section 430b shows the respective valence band Vb and conductive band Cb of well layer 330b. The driver 420b displays the valence band Vb and the conductive band Cb of the strained hole blocking layer (HBL) 320b. And the section 420a shows the valence band Vb and the conductive band Cb of the strain-free hole blocking layer 320a.

In the example of Figures 3 and 4, layers 320 to 340 are formed from materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system. More specifically, the strain barrier layer structure 330a-1 and the electron blocking layer 340a are each formed from a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, wherein the aluminum ratio of the material exceeds 53% ( 0.53<x<1) and the indium ratio is less than 49% (0<y<0.49). The presence of greater than 53% aluminum in layers 330a and 340a causes the conductive band Cb of those layers to be defined by the energy of their Increased relative to the conductive strip. As mentioned above, the increase in the X-band energy of the strain barrier layer structure 330a-1 and the electron blocking layer 340a widens their respective band gaps and enhances their electron blocking capabilities.

The increase in X-band energy of the strain barrier layer structure 330a-1 is shown in sections 440a and 430a of the energy band diagram 400. Each of these segments exhibits a jump in X-band energy that is not present in segments 240a and 230b of energy band diagram 200. It is apparent that each jump in X-band energy is caused by the presence of a respective strain barrier layer structure 330a-1, as shown in the figure. It should be recalled that sections 240 and 230b of the energy band diagram 200 show the X-band energies of the unstrained barrier layer 120a and the unstrained electron blocking layer (EBL) 140, while sections 440a and 430a show the tensile strained barrier layer structure 330a-1 and the X-band energy of the tensile strained electron blocking layer (EBL) 340a. Thus, sections 440a and 430a illustrate the increase in X-band energy (and therefore conductive band energy) that occurs when tensile strain is induced in materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system. As described above, stretching of barrier layer structure 330a-1 and electron blocking layer 340a is induced by maintaining the indium ratio below 49% (0<y<0.49) while growing layers 330a and 340a on a GaAs substrate. Strain.

Also shown in FIG. 4 are the conductive band compensation CBO ₁ of the strained electron barrier layer 440 a and the conductive band compensation CBO ₂ of the strained barrier layer structure 330 a - 1 . As shown in the figure, the increase in the X-band energy of the strained electron blocking layer 440a and the strained barrier layer structure 330a-1 increases their respective conductive band compensation, thereby enhancing their ability to prevent electrons from escaping the active layer 330 and within the active layer 330. Capabilities of individual well structures.

In the examples of Figures 3 and 4, the strained hole blocking layer 320b is formed of a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, in which the indium ratio is higher than 49% (0.49<y <1). Increasing the indium ratio above 49% induces compressive strain in the lattice of hole blocking layer 320b, which in turn causes a reduction in its valence band energy Vb. The decrease in valence band energy relative to the valence band edge of the quantum well is plotted in section 420b of the energy band diagram 400 . As depicted in section 420b, the valence band energy of compressively strained HBL 320b only decreases relative to the valence band energy of unstrained HBL 320a. This is in contrast to region 220 of energy band diagram 200, which shows the energy drop visible in the energy deficient region 420b of the valence band of HBL 120. As discussed above, the reduction in the valence band energy of the hole blocking layer 320b enhances its hole blocking capability so that the device 300 is more suitable for use in high temperature and/or high current applications.

In addition, the valence band compensation VBO _s of the strained hole blocking layer 320b is shown in FIG. 4 . As shown in the figure, the reduction in valence band energy of the hole blocking layer 320b results in an increased valence band compensation and an enhanced ability to prevent holes from overflowing from the active layer 330.

Briefly, in the example of FIGS. 3 and 4 , device 300 forms a light emitting device by epitaxially growing layers 320 a to 340 b on a substrate 310 along an axis perpendicular to the plane of the substrate, the axis extending from the substrate. The plane extends towards layer 340. Each of layers 320a-340b is characterized by a respective thickness, which is the width of the layer along the growth axis. In the examples of FIGS. 3 and 4 , the substrate 310 includes a GaAs substrate. HBL 320a is formed over substrate 310 and includes one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy series, where (0.4<x<1.00) and (y=0.49). In some embodiments, HBL 320b can have a thickness in the range of 0 nm to 1000 nm. HBL 320b is formed over HBL 320a and includes one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, where (0.4&lt;x&lt;1.00) and (0.49&lt;y&lt;0.7). In some embodiments, HBL 320b can have a thickness in the range of 0 nm to 1000 nm. In some embodiments, the thickness of HBL 320b may be lower than the critical thickness of the material from which it is formed to avoid sagging.

Barrier layer 330a is formed over HBL 320b and may have a thickness in the range of 1 nm to 1000 nm. Each of the barrier layers 330a may include one or more strained structures 330a-1 and/or one or more unstrained structures 330a-2. Each strained structure 330a-1 may be formed from a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family, where the aluminum ratio of the material exceeds 53% (0.53<x<1) and the indium ratio is less than 49 % (0＜y＜0.49). The thickness of the strained structure may be less than the critical thickness of the material forming the strained structure to avoid relaxation. Each strain-free barrier layer structure 330a-2 may be formed from one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, where (y=0.49) and (0.4<x<1). Additionally, as described above, any of the barrier layers 330a may include one or more strained structures. The strained layer may be composed of multiple layers with different amounts of strain or graduated strain across the strained layer. The well layers 330b and the barrier layers 330a are staggered to form a plurality of well structures. Any of the well layers 330b may include a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy series, where (0&lt;x&lt;0.3) and (0&lt;y&lt;0.49). In some embodiments, any of the well layers 330b may have a thickness in the range of 1 nm to 100 nm.

EBL 340a is formed over barrier layer 330a and well layer 330b and may include a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, where (0.53<x<1.00) and (0.2<y< 0.49). In some embodiments, EBL 340a may have a thickness in the range of 0 nm to 1000 nm. In some embodiments, the thickness of EBL 340a may be within the critical thickness of the material forming EBL 340a to avoid sagging. EBL 340b is formed over EBL 340a and includes one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, where (0.40&lt;x&lt;1.00) and (y=0.49). In some embodiments, EBL 340b can have a thickness in the range of 0 nm to 1000 nm.

In this example, layers 320a-320b are part of the lower confinement layer (LCL) of device 300, while layers 340a-340b are part of the upper confinement layer (UCL) of device 300. However, in some implementations, any of layers 320a-320b and 340a-340b may be separate from the LCL and UCL of device 300. Although in this example, the hole blocking layers 320a to 320b are formed closer to the substrate 310 than the electron blocking layers 340a to 340b; Alternative embodiments are possible. Additionally or alternatively, in some implementations, any of layers 320a - 320b may be part of the UCL of device 300 and any of layers 340a - 340b may be part of the LCL of device 300 .

In addition, it should be noted that the thickness ranges, aluminum ratios, and indium ratios described above are only examples. Furthermore, it should be noted that alternative embodiments are possible in which one or more of the layers discussed above are omitted. Non-limiting examples of such embodiments are discussed further below with respect to Figures 5-7.

Figure 5 depicts an example of a light emitting device 500 in accordance with aspects of the invention. As shown in the figure, the device 500 includes a substrate 510, a (n-type) hole blocking layer (HBL) 520, an active layer 530, a (p-type) electron blocking layer (EBL) 540 and each formed on the EBL. Contacts 550a and 550b on 540 and HBL 520. Substrate 510 may include a GaAs substrate or any suitable type of substrate. HBL 520 is formed over substrate 510 and its lattice can be compressively strained. HBL 520 may include one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family and/or any suitable type of material. When _HBL 520 includes _one of _the materials from the ( _Al Strain accumulates. In some embodiments, the thickness of the compressively strained HBL may be less than the critical thickness of the material of the layer to avoid relaxation that would create defects in the crystal.

Active layer 530 is formed over HBL 520 . Active layer 530 may be formed from a material having an ( _{AlxGa1 -x} ) _{1- yInyP} composition and/or any other suitable type of material. In this example, the active layer 530 has a homogeneous structure, but alternative embodiments are possible in which the structure of the active layer 530 is heterogeneous. An electron blocking layer (EBL) 540 is formed over the active layer 530 . EBL 540 may include one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family and/or any other suitable type of material. Although in this example EBL 540 has a homogeneous structure, alternative embodiments are possible in which the structure of EBL 540 is heterogeneous. Although the EBL 540 is unstrained in this example, alternative embodiments are possible in which tensile strain is induced in the lattice of the EBL 540.

Figure 6 depicts an example of a light emitting device 600 in accordance with aspects of the invention. As shown in the figure, the device 600 includes a substrate 610, a (n-type) hole blocking layer (HBL) 620, an active layer 630, a (p-type) electron blocking layer (EBL) 640 and each formed on the EBL Contacts 650a and 650b on 640 and HBL 620. Substrate 610 may include a GaAs substrate or any other suitable type of substrate. A hole blocking layer (HBL) 620 is formed above the substrate 610 . HBL 620 may be formed from one of the materials from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family and/or any other suitable type of material. Although in this example HBL 620 has a homogeneous structure, alternative embodiments are possible in which HBL 620 has a heterostructure. Although the HBL 620 is unstrained in this example, alternative embodiments are possible in which the crystal lattice of the HBL 620 is induced to have a compressive strain. Active layer 630 is formed over HBL 620 and may be formed from a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system and/or any other suitable type of material. An electron blocking layer (EBL) 640 is formed over the active layer 630 . Electron blocking layer (EBL) 640 may include a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family and/or any other suitable type of material. Although in this example EBL 640 has a homogeneous structure, alternative embodiments are possible in which the structure of EBL 640 is heterogeneous. Although the EBL 640 is unstrained in this example, alternative embodiments are possible in which tensile strain is induced in the lattice of the EBL 640.

According to the example of FIG. 6, the active layer 630 includes a plurality of barrier layers 630a and a plurality of well layers 630b configured to form a plurality of well structures. Each well structure may include a well layer 630b disposed between two strain barrier layers 630a. Each of _the barrier layers may be made of a material _{from the} ( _Al of materials formed. As discussed above, the presence of less than 49% indium in the composition of barrier layer 630a can lead to the accumulation of tensile strain in its respective crystal lattice, which in turn can widen the band gap of barrier layer 630a and enhance its electron blocking capabilities. Although in this example each of the barrier layers 630a includes a single strained structure, alternative embodiments are possible in which each of the barrier layers 630a includes both a strained structure and an unstrained structure.

Figure 7 depicts an example of a light emitting device 700 in accordance with aspects of the invention. As shown in the figure, device 700 may include a substrate 710, a (n-type) hole blocking layer (HBL) 720, an active layer 730, a (p-type) tensile strained electron blocking layer (EBL) 740, and Contacts 750a and 750b are formed on EBL 740 and HBL 720 respectively.

Substrate 710 may include a GaAs substrate or any suitable type of substrate, such as, for example, a Si substrate. HBL 720 is formed over substrate 710 and may include a material from the ( _{AlxGa1 -x} ) _{1- yInyP} alloy family and/or any suitable type of material. Active layer 730 forms above the hole blocking layer. Active layer 730 may be formed from a material having an ( _{AlxGa1 -x} ) _{1- yInyP} composition and/or any other suitable type of material. In this example, active layer 730 has a homogeneous structure, but alternative embodiments are possible in which the structure of active layer 730 is heterogeneous. EBL 740 is formed over active layer 730 . EBL ₇₄₀ may include _a material from _{( Al} A material in the alloy system. As discussed above, the presence of less than 49% indium in the composition of EBL 740 can lead to the accumulation of tensile strain in its crystal lattice, which in turn can enhance its electron blocking capabilities. Although in this example, EBL 740 has a heterogeneous structure, alternative embodiments are possible in which the structure of EBL 740 is heterogeneous.

Figures 1 to 7 are for illustration only. At least some of the elements discussed with respect to these figures may be arranged in a different order, combined, and/or omitted entirely. It should be understood that clauses providing examples described herein and phrases such as "such as," "for example," "including," "in some aspects," "in some embodiments," and the like should not be construed. The subject matter disclosed is limited to the specific examples.

Although the examples provided in the present invention are described in the context of the ( _{AlxGa1 -x} ) _{1- yInyP} alloy system, it should be noted that the present invention is not limited only to this system. Furthermore, although in the above examples the hole blocking layer is grown closer to the substrate than the electron blocking layer, alternative embodiments are possible in which the electron blocking layer is grown closer to the substrate than the hole blocking layer.

Although embodiments have been described in detail, those skilled in the art will appreciate that modifications may be made in view of the invention without departing from the spirit of the inventive concepts described herein. In particular, different features and components of the different devices described herein may be used in any of the other devices, or features and components may be omitted from any of the devices. A feature of a structure described herein within one embodiment may be applied to any embodiment. Therefore, the scope of the invention is not intended to be limited to the specific embodiments illustrated and described.

Although features and elements are described above in specific combinations, one of ordinary skill will understand that each feature or element may be used alone or in any combination with other features and elements. Additionally, the methods described herein may be implemented in a computer program, software, or firmware incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include (but are not limited to) a read-only memory (ROM), a random-access memory (RAM), a temporary register, cache memory, semiconductor memory devices, magnetic media ( such as internal hard drives and removable disks), magneto-optical media and optical media (such as CD-ROM disks and digital versatile discs (DVD)).

100‧‧‧Light-emitting device 110‧‧‧Substrate 120‧‧‧Strain-free hole blocking layer (HBL) 130‧‧‧Active layer 130a‧‧‧Barrier layer 130b‧‧‧Well layer 140‧‧‧Electron blocking layer ( EBL) 150a‧‧‧Contact 150b‧‧‧Contact 200‧‧‧Energy Band Diagram 220‧‧‧ Section 230a‧‧‧Section 230b‧‧‧Section 240‧‧‧Section 300‧‧‧Emit light Device 310‧‧‧Substrate 320‧‧‧Lower confinement layer (LCL) 320a‧‧‧Unstrained HBL320b‧‧‧Compressive strain HBL330‧‧‧Active layer 330a‧‧‧Strain barrier layer 330a-1‧‧‧Strain barrier layer Structure 330a-2‧‧‧Strainless barrier layer Structure 330b‧‧‧Well layer 340‧‧‧Upper confinement layer (UCL) 340a‧‧‧Tensile strain EBL340b‧‧‧No strain EBL400‧‧‧Energy band diagram 420a‧ ‧‧Section 420b‧‧‧Section 430a‧‧‧Section 430b‧‧‧Section 440a‧‧‧Section 440b‧‧‧Section 500‧‧‧Light-emitting device 510‧‧‧Substrate 520‧‧‧ HBL530 ‧‧‧Active layer 540‧‧‧EBL550a‧‧‧Contact 550b‧‧‧Contact 600‧‧‧Light-emitting device 610‧‧‧Substrate 620‧‧‧HBL630‧‧‧Active layer 630a‧‧ ‧Barrier layer 630b‧ ‧‧Well layer 640‧‧‧EBL650a‧‧‧Contact 650b‧‧‧Contact 700‧‧‧Light-emitting device 710‧‧‧Substrate 720‧‧‧Hole blocking layer (HBL) 730‧‧‧Active layer 740‧ ‧‧Tensile strain electron barrier layer (EBL) 750a‧‧‧Contact 750b‧‧‧Contact Cb‧‧‧ Conductive tape CBO ₁ ‧‧‧Conductive tape compensation CBO ₂ ‧‧‧Conductive tape compensation Vb‧‧‧Valence With VBO ₁ ‧‧‧Valence band compensation VBO ₂ ‧‧‧Valence band compensation VBO _s ‧‧‧Valence band compensation

A more detailed understanding may be obtained from the following description, given by way of example in conjunction with the accompanying drawings, in which like reference numerals refer to like elements, and in which:

Figure 1 is a cross-sectional view of an example of a light-emitting device according to an aspect of the present invention;

FIG. 2 is an energy band diagram of the light-emitting device of FIG. 1 according to an aspect of the present invention;

Figure 3 is a cross-sectional view of an example of a light-emitting device according to an aspect of the present invention;

Figure 4 is an energy band diagram of the light-emitting device of Figure 3 according to an aspect of the present invention;

Figure 5 is a cross-sectional view of an example of a light-emitting device according to an aspect of the present invention;

Figure 6 is a cross-sectional view of an example of a light-emitting device according to aspects of the present invention; and

7 is a cross-sectional view of an example of a light emitting device according to aspects of the present invention.

700:Lighting device

710:Substrate

720: Hole blocking layer (HBL)

730:Active layer

740‧‧‧Tensile strained electron blocking layer (EBL)

750a‧‧‧Contact

750b‧‧‧Contact

Claims (20)

A light emitting device comprising: an electron blocking layer, wherein a first portion of the electron blocking layer is configured to have a tensile strain and a second portion of the electron blocking layer is configured not to have a tensile strain; a a hole blocking layer, wherein a first portion of the hole blocking layer is configured to have a compressive strain and a second portion of the hole blocking layer is configured not to have a compressive strain; and an active layer disposed on between the hole blocking layer and the electron blocking layer, wherein the first portion of the electron blocking layer is between the second portion of the electron blocking layer and the active layer, and wherein the third portion of the hole blocking layer A portion is between the second portion of the hole blocking layer and the active layer. The light-emitting device of claim 1, wherein the hole blocking layer has a composition expressed as (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4

x

1 and 0.49

y

0.7. The light-emitting device of claim 1, wherein the electron blocking layer is formed of a first material from the AlGaInP family, and the hole blocking layer is formed from a second material from the AlGaInP family, the second material having An indium ratio greater than that of the first material. The light-emitting device of claim 1, wherein: the hole blocking layer includes a first n-type layer and a second n-type layer, the first n-type layer is strain-free, and the second n-type layer is compressively strained . The light-emitting device of claim 4, wherein the first n-type layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4

x

1 and y=0.49. The light-emitting device of claim 1, wherein the electron blocking layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4<x<1 and 0.2<y<0.7. The light-emitting device of claim 1, wherein: the electron blocking layer includes a first p-type layer and a second p-type layer, the first p-type layer is strain-free, and the second p-type layer is configured to have A tensile strain. The light-emitting device of claim 1, further comprising a GaAs substrate, wherein: the hole blocking layer, the electron blocking layer and the active layer are formed on the same side of the GaAs substrate, and the hole blocking layer, the electron blocking layer The barrier layer and the active layer are each formed from a respective material from the AlGaInP family. A light-emitting device comprising: an electron blocking layer; a hole blocking layer, wherein at least a portion of the hole blocking layer is configured to have a compressive strain; and an active layer disposed between the hole blocking layer and the hole blocking layer Between the electron blocking layers, the active layer includes a first barrier layer configured to have a tensile strain, a first barrier layer configured to have a tensile strain a second barrier layer and a well layer disposed between the first barrier layer and the second barrier layer. The light-emitting device of claim 9, wherein the hole blocking layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4

x

1 and 0.49

y

0.7. A light-emitting device comprising: an electron blocking layer, wherein at least a portion of the electron blocking layer is configured to have a tensile strain; a hole blocking layer, wherein at least a portion of the hole blocking layer is configured to have a compressive strain strain; and an active layer formed between the hole blocking layer and the electron blocking layer, the active layer including at least one well structure including a first barrier layer configured to have a tensile strain , a second barrier layer configured to have a tensile strain and a well layer disposed between the first barrier layer and the second barrier layer, wherein the electron blocking layer is an upper confinement layer of the light emitting device and The hole blocking layer is part of one of the lower confinement layers of the light emitting device, and the hole blocking layer is part of the other of the upper confinement layer of the light emitting device and the lower confinement layer of the light emitting device. The light-emitting device of claim 11, wherein the hole blocking layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4<x<1 and 0.49<y<0.7 . The light-emitting device of claim 11, wherein: the hole blocking layer includes a first n-type layer and a second n-type layer, the first n-type layer is unstrained, and the second n-type layer is compressively strained, And the first n-type layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0

x

1 and 0.49

y

1. The light-emitting device of claim 11, wherein the electron blocking layer has a composition represented by (Al _x Ga _(1-x) ) _1-y In _y P, where 0.4

x

1 and 0.2

y

0.7. The light emitting device of claim 11, wherein the electron blocking layer includes a first unstrained p-type layer and a second p-type layer configured to have a tensile strain. A light emitting device comprising: an electron blocking layer, a first portion of which is configured to have a tensile strain and a second portion of the electron blocking layer is configured to not have a tensile strain; a hole blocking layer , which includes a first unstrained n-type layer and a second n-type layer configured to have a compressive strain; and an active layer formed between the hole blocking layer and the electron blocking layer, wherein the The first n-type layer is formed from a first material from the family of AlGaInP, the second n-type layer is formed from a second material from the family of AlGaInP, the second material having a greater an indium ratio, and wherein the first portion of the electron blocking layer is between the second portion of the electron blocking layer and the active layer, and wherein the second n-type layer is between the first n-type layer and the active layer between layers. The light emitting device of claim 16, wherein the second n-type layer is positioned closer to the active layer than the one n-type layer, and the indium ratio of the second material is greater than 0.49. The light emitting device of claim 16, wherein the second n-type layer has a thickness less than a critical thickness associated with the second material. The light emitting device of claim 16, wherein the electron blocking layer includes a first unstrained p-type layer and a second p-type layer configured to have a tensile strain. A light emitting device comprising: an electron blocking layer; a hole blocking layer including a first unstrained n-type layer and a second n-type layer configured to have a compressive strain; and a An active layer formed between the hole blocking layer and the electron blocking layer, the active layer including at least one well structure including a first barrier layer configured to have a tensile strain, configured to A second barrier layer having a tensile strain and a well layer disposed between the first barrier layer and the second barrier layer, and the first barrier layer and the second barrier layer have a structure represented by (Al _x A composition of Ga _(1-x) ) _1-y In _y P, where 0.4<x<1 and 0<y<0.49, wherein the first n-type layer is formed from a first material from the system of AlGaInP , and the second n-type layer is formed from a second material from the system of AlGaInP, the second material having a greater indium ratio than the first material.